大西洋热盐环流与气候突变

Atlantic Thermohaline Circulation and Abrupt Climate Changes

未来是否会发生由大西洋热盐环流崩溃引起的气候突变是目前极富争议性的全球气候变化问题。首先回顾了过去发生的气候突变事件以及若干成因假说,介绍了McGill地球系统模拟组的有关研究成果,并探讨了过去气候突变事件中的南北半球遥相关,最后讨论了未来是否会发生大西洋热盐环流崩溃引起的气候突变。对过去发生的大西洋热盐环流突变的研究表明,它产生的气候背景与现代气候以及将来进一步变暖的气候截然不同,因此不能凭过去发生过的突变事件来推论将来会发生类似的气候突变。尽管有的气候模式预测全球变暖会导致大西洋热盐环流减弱甚至崩溃而引发气候突变,但是目前全球气候系统的观测有许多不足之处,并且现代气候模式也存在较大的不确定性,因此尚不能确信现在的全球变暖会导致这样的气候突变。

It is a highly controversial issue that there will be an abrupt and large climate change induced by the reorganization of the Atlantic thermohaline circulation in a warming climate. In order to understand this issue, the past abrupt climate change events and some hypotheses on the causes are first reviewed. Some recent research results from the McGill Earth System Modelling group on the past abrupt climate changes are then presented. Also, Southern-Northern Hemispheric teleconnections related to the reorganization of the Atlantic thermohaline circulation are summarized. Lastly, a discussion on our ability to predict such a future abrupt climate change is also given. The studies on the past abrupt thermohaline circulation changes show that the background climates that are responsible for past abrupt thermohaline circulation changes are different from the modern climate and the future warm climate. Therefore, it is not possible to conclude that there will be such a future abrupt climate change, based on paleoclimate studies. Although some climate models predict that the Atlantic thermohaline circulation will be weakened or even shut down by increased atmospheric CO2 levels, we are still not sure that such an abrupt climate change will happen because more observational data are needed for us to validate model results and there are significant uncertainties in climate models.